1) Peel and cube the butternut squash.
2) Coarsely chop the onion.
3) Peel and smash the garlic clove.
4) Chop the carrot into 1/2 inch chunks.
5) In a large stock pot, add all of the vegetables and the vegetable stock.
6) Bring to a boil, cover, lower the temperature and simmer until the squash is soft -- 20-25 minutes.
7) Drain the vegetables in a colander (save the liquid for soup).
8) In 3-5 batches, put a portion of the vegetables into a food processor and drizzle in 1-2 tablespoons of olive oil. Process until it is very smooth.
9) Transfer the butternut squash butter to a large bowl.
10) Stir in the salt and adjust to taste.